Add quick-launch bar feature

[wallstop]

This commit implements a FlowLauncher/ULauncher-style quick-launch bar that can be toggled with shift+space. Key features:

• New TerminalState.OpenLauncher state for launcher mode
• New TerminalControlTypes.ToggleLauncher control type
• Shift+space hotkey to toggle launcher (configurable)
• Centered popup with configurable width (default 50% screen width)
• Dynamic height that scales based on:
  • Base launcher height (configurable)
  • Number of visible history items (up to configurable max)
  • Number of active autocomplete items
• Height automatically adjusts when autocomplete suggestions change
• Minimal height when no history/autocomplete active
• Properly handles window positioning and sizing

Configuration options in TerminalUI inspector:

• launcherWidth: Width ratio (0.2-1.0)
• launcherBaseHeight: Base height in pixels (100-600)
• launcherHistoryItemHeight: Height per history item (20-100)
• launcherMaxHistoryItems: Max history items to show (1-10)
• launcherAutoCompleteItemHeight: Height per autocomplete item (20-100)